ICOS ERIC is a pan-European research infrastructure that provides standardised and open data on the atmospheric composition for greenhouse gases, green house gas exchange fluxes between terrestrial ecosystems and the atmosphere, and CO2 partial pressure at water surfaces. The Carbon Portal is the data discovery and access portal of ICOS. It offers free access to all ICOS observational data, elaborated data products from ICOS end user communities, as well as to scientific and educational products and services. The main target audiences of the Carbon Portal are researchers from environmental and earth science disciplines, such as studies of atmospheric composition, climate, ecosystem functioning, micrometeorology, physical geography and remote sensing. In addition to providing user-friendly (and machine-friendly) internet- and other computer-network based interfaces, the Carbon Portal organises long-term archiving of ICOS data products to guarantee their safe storage, future access and easy re-use. ICOS is committed to following data repository and curation best practices, including the FAIR principles All ICOS data products are offered under a Creative Commons Attribution license (CC-BY) to all users who accept the ICOS Data Policy. The Carbon Portal is co-hosted by Lund University in Sweden and Wageningen University in the Netherlands.